Carbon monoxide alarms are now recommended or required for use in residential houses in many jurisdictions in North America, particularly for houses which are heated by natural gas or oil furnaces. Carbon monoxide alarms typically comprise a CO (carbon monoxide) sensor and associated electronics housed in a compact casing, which may be ac or battery operated. CO alarms are designed to respond when the concentration of carbon monoxide exceeds certain preset values over preselected periods of time. For example, the Underwriters Laboratories Standard UL 2034, based upon 10 percent carboxyhemoglobin, requires a CO alarm to sound when the CO concentration exceeds 70 ppm (parts per million) for 240 minutes, or 150 ppm for 50 minutes, or 400 ppm for 15 minutes.
Carbon monoxide alarms are reliable, and they typically include test circuits which allow the consumer to test the electronics. Nevertheless, many consumers have expressed a desire to satisfy themselves that the CO alarm will generate an alarm signal, in the presence of a harmful concentration of carbon monoxide gas.
Consumers have been known to "test" CO alarms by placing them adjacent the exhaust pipe of an automobile, for a period of time. However, this form of testing is generally not effective, since automobile exhaust gas is dirty, and tends to contaminate the CO sensor.
There is a CO alarm testing kit currently available in the marketplace, comprising a glass vial of CO gas and a plastic bag. To test an ac operated CO alarm using this testing kit, the user must plug the alarm into an extension cord, place the alarm and the vial into the bag, close the bag around the extension cord, and break the vial. This testing kit is not always effective, because sometimes the vial leaks, and it is difficult to determine if the vial is full or empty, because CO gas is colourless. This kit is somewhat awkward for use with ac operated alarms, since it requires the user to hold the bag tightly around the extension cord for a period of time. This kit is also relatively expensive, and can be used only once.
There is accordingly a need for an improved CO alarm testing device, which overcomes the disadvantages of the prior art.